Due to a global warming phenomenon, proposals for reduction of greenhouse gas are now releasing in various countries of the world. Among those, the Korean Government has established the goal of 37% decrease in greenhouse gas, compared to the estimated exhaust for 2030, thus increasing a burden on the industry.
As one of the important alternative ideas to reduce the greenhouse gas, using exhausted carbon dioxide as a resource (“resourcing”) becomes a more significant topic of conversation, instead of decreasing a carbon dioxide exhaust amount. There are diverse proposals for resourcing carbon dioxide and one of them is to prepare a synthetic gas through a reforming reaction of methane using carbon dioxide. The reforming reaction of methane using carbon dioxide has an advantage such that carbon dioxide and methane as causes of the global warming could be simultaneously eliminated. In addition, compared to other reforming methods, a synthetic gas having a relatively higher content of carbon monoxide (H2:CO=1:1) could be prepared. Therefore, the produced synthetic gas may be used as a reactant in a process for production of high-value added chemical products such as oxoalcohol, dimethyl ether (DME), poly carbonate (PC), acetic acid, etc.
Such a carbon dioxide reforming reaction is a strong endothermic reaction wherein a theoretical maximum conversion rate at a predetermined temperature, that is, an equilibrium conversion rate is increased at a higher temperature, and thus the reaction occurs at a temperature of 650° C. or more, and is generally progressing at a high temperature of 850° C. However, the reaction at the high temperature described above enables catalyst particles to be easily sintered, thus decreasing a point of activation (“activation point”) of catalyst, while simultaneously occurring carbon deposition significantly deteriorates catalytic activity. Consequently, it is necessary to develop a reforming catalyst with improved thermal durability.
In particular, although a monolith catalyst capable of processing a great amount of greenhouse gas during the reforming reaction and having high mechanical and thermal durability is required, prior art documents have mostly focused on inventions for improvement of performance of the monolith catalyst.
With regard to a conventional reforming reaction catalyst, Korean Patent Registration No. 10-1480801 proposes a method of manufacturing a monolith catalyst for reforming reaction of methane using carbon dioxide, which includes: mixing and carrying a metal precursor solution with a carrier; coating a monolith support with the mixed and carried solution then drying the same; and calcining the monolith support coated with the mixed and carried solution.
However, the above-described monolith catalyst can maintain high activity for a relatively longer period of time than the existing granular type forming catalysts, thereby enabling production of a stable synthetic gas. Due to structural features of monolith, a pressure loss is relatively low and a reaction at a high flow rate may proceed. However, the above problems, that is, carbon deposition and non-activation of a catalyst due to the degradation under a high temperature reaction condition (800° C. or more) have not yet been overcome.
Further, Korean Patent Registration No. 10-0719484 proposes a catalyst having a water vapor reforming structure, wherein a nickel-based water vapor reforming catalyst containing nickel; alumina; and one or two basic solids selected from a group consisting of magnesium oxide and potassium is applied to and coated on a metal monolith made of iron, stainless steel or iron-chromium-aluminum alloy (Fecralloy).
Korean Patent Laid-Open Publication No. 10-2015-0087341 discloses a sectional-catalyzed substrate monolith which includes a first section and a second section: wherein the first section and second section are arranged in series in an axial direction; and the first section includes a platinum metal carried in a support, and a first base metal oxide selected from a group consisting of iron oxide, manganese oxide, copper oxide, zinc oxide, nickel oxide and a mixture thereof or a first base metal selected from a group consisting of iron, manganese, copper, zinc, nickel and a mixture thereof carried in an inorganic oxide, while the second section includes copper or iron carried in zeolite, and a second base metal oxide selected from a group consisting of iron oxide, manganese oxide, copper oxide, zinc oxide, nickel oxide and a mixture thereof or a second base metal selected from a group consisting of iron, manganese, copper, zinc, nickel and a mixture thereof carried in an inorganic oxide; and the second base metal is different from the first base metal.
Further, Korean Patent Registration No. 10-1038242 discloses an improved catalyst for oxidizing alkane or a mixture of alkane and alkene into corresponding unsaturated carboxylic acid through vapor-phase catalyst oxidation, and in particular, proposes a method for improving performance of a catalyst that includes: at least one element selected from a group consisting of Nb, Ta, W, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Ag, Sb, I, B, In and Ce; and a ceramic foam, ceramic monolith or ceramic fabric.
However, these catalysts also have not yet basically solved the above-described problems occurring during the reforming reaction.